Several electrical valve actuators are presently available in the marketplace. In most pool and spa applications, it is desirable to have a highly efficient and powerful valve actuator. Actuators presently available on the market use a low voltage inductive motor or a stepper motor to drive the actuator. The low voltage AC inductive motor is very inefficient, low in torque, and very heavy. In many cases, the seal of the valve diverter will swell after a period of use. When seal swelling occurs, the AC inductive motor will stall, and the result will be a high power drain, and a burned motor or potential damage to the circuits supplying power to the motor.
A stepper motor for use as an actuator of a diversion valve is an improvement over the AC inductive motor. The stepper motor has a permanent magnet rotor that reacts to the reversing magnetic induction from the stator. The stepper motor, as the name implies, produces incremental angular rotation in accordance with the number of poles on the stator and the energization sequence of the stator windings. The number of poles corresponds with the angle of movement per step. In the swimming pool and spa industry, the stepper motor typically used is a low speed motor, which reacts to the 60 cycles of the AC line power supply. Timing, speed, and direction of travel is generally dictated by a capacitor. The frequency of the AC power supply also limits the speed of the motor to 360 rpm or 1 revolution per every 10 input signal cycles or wavelengths. The stepper motor typically drives a set of gears to reduce the speed and increase the torque capability of the actuator. A 360 to 1 gear ratio will give the actuator enough torque to rotate the valve diverter 180.degree. in 30 seconds. The stepper motor is a better alternative to the AC inductive motor. This is indicated in view of the industry movement towards use of the stepper motor and phasing out use of the AC motor.
Even though the stepper motor has a good acceptance in the swimming pool industry, it is not an efficient motor. Power comsumption is 700 milliamps compared to 180 milliamps of a DC motor. Similar to the AC inductive motor, the stepper motor is also susceptible to a stalled situation if the diverter seal swells thereby increasing the force required to rotate the diverter within the valve body.
The cost to produce both the AC inductive motor, and the stepper motor is considerably high. The cost is primarily related to the amount and cost of materials involved, specialized construction, and production volume. A DC motor, on the other hand, is a very inexpensive motor, particularly because many are used in numerous applications, specifically battery powered applications. Manufacturers produce DC motors by the millions every day. Many of the manufactures in several countries are intense in competing for customers in the DC motor market. Another advantage of a DC motor over an AC motor is its ability to reverse the direction of rotation without the need for additional rotor windings.
A DC motor actuated flow diversion valve which consumes less power, produces a higher torque level for moving a diverter within a valve, and is readily substituted for present AC motor driven valves is needed.